Wedbush analyst Michael Pachter estimates that Nintendo sold about 2.6 million Wii units last month, helping it to once again secure the top spot in hardware sales. The analyst believes it was trailed by the Xbox 360's 2.5 million unit sales and the PlayStation 3's 1.2 million unit sales.

But that's not quite the whole story on December.

If Nintendo did in fact sell 2.6 million Wii units, that means it saw a 32 percent decline compared with December 2009. Sony's PlayStation 3 would have seen unit sales decline 12 percent year over year. And with 2.5 million unit sales, the Xbox 360 would have seen 91 percent growth compared with December 2009.

Nintendo might have experienced bad news on the portable front as well. Pachter believes Nintendo sold 2.55 million DS units in December, representing a 23 percent decline year over year.

Overall, Pachter estimates that unit sales of game hardware industrywide were down 12 percent in December, compared with the prior year.

Pachter examines the retail channel each month and delivers sales forecasts, based on his data, prior to NPD releasing its official count. NPD is expected to make December sales figures available on Thursday.

Assuming Pachter's estimates are correct, they top off an extremely difficult year for Nintendo, which had easily bested the competition since the Wii's launch in 2006.

Throughout the year, Nintendo struggled to push hardware on consumers. During the six-month period ended that September 30, the company posted a $24.6 million loss on poor Wii and DS sales. It sold 6.69 million DS units and 4.97 million Wii units in that period. During the same six-month period in 2009, it sold 11.7 million DS units and 5.75 million Wii units.

For its part, Nintendo has kept a brave face on the trailing sales. The company has said that it had another banner year in 2010, selling over 7 million units of its Wii console for the third-consecutive time. However, it failed to mention that in 2008, it sold over 10 million Wii units and nearly hit the 10 million milestone again in 2009.

On the portable side, Nintendo has acknowledged that DS sales are lower than they were in 2009 but expects that its upcoming 3DS platform, which allows gamers to play titles in 3D without glasses, to help buoy sales. Nintendo President Satoru Iwata said yesterday that he expects Nintendo to sell 4 million 3DS units by March, but acknowledged that potential health issues related to the device--namely, its potential to harm the vision of children under the age of 6--could have a negative effect on earnings.

Nintendo's 3DS launches in Japan on February 26 for $300. It's expected to be released in the U.S. in March.